Oxidative transformation of aryls using molybdenum pentachloride

The Coordination and Bioinorganic Chemistry of Molybdenum

A series of oxomolybdate(v) complexes with methanol was prepared by the reaction of (PyH) 5 [MoOCl 4 (H 2 O)] 3 Cl 2 (1) or (PyH)[MoOBr 4 ] (PyH + = pyridinium cation, C 5 H 5 NH + ) in methanol. (PyH) 2 [MoOCl 4 (MeOH)]Cl (2) is obtained upon substitution of coordinated water for methanol in 1. Small amounts of weak bases such as pyridine or trifluoroacetate promote further substitution chemistry at the labile sites, followed by dimerisation to the well-known {Mo 2 O 4 } 2 + core. A dinuclear anion with coordinated methanol can be isolated as its pyridinium salt, (PyH) 2 [Mo 2 O 4 Cl 4 (MeOH) 2 ], in two crystalline modifications, either as a triclinic (3) or as an orthorhombic polymorph (4). After prolonged reaction times further assembly of dinuclear fragments takes place and tetranuclear [Mo 4 O 8 (OMe) 2 (MeOH) 2 Cl 4 ] 2 - is formed. The products of the analogous reactions with (PyH)[MoOBr 4 ] as the starting material depend largely upon the reaction temperature. Dinuclear (PyH) 2 [Mo 2 O 4 Br 4 (MeOH) 2 ] (5), which crystallises in an orthorhombic unit cell and whose structure is isotypic to that of 4, is obtained only if the reaction takes place at low temperature (5 °C); under ambient conditions (PyH) 2 (Mo 4 O 8 (OMe) 2 -(MeOH) 2 Br 4 ] (6) is obtained instead. The tetranuclear anion of 6 consists of a commonly adopted assembly of two {Mo 2 O 4 } 2 + units. The identity of the products was determined by infrared spectroscopy and X-ray structure analyses.

Novel Methanol-Containing Oxomolybdate(V) Complexes: Synthesis and Structural Characterisation of Intermediates in the Formation of {Mo2O4}2+ Clusters from [MoOCl4(H2O)]– and [MoOBr4]– Precursors

Coordination compounds of molybdenum

Cationic polymerization of vinyl ether (VE) was examined with methanol/metal chloride initiating systems instead of those with the conventionally used VE−protonic acid adduct initiators. With MoCl5, a highly oxophilic metal halide, the polymerization of isobutyl VE (IBVE) using methanol proceeded in a living fashion in the presence of ethyl acetate, although the reaction was not controlled in conjunction with IBVE−HCl adduct. Furthermore, in the methanol-initiated polymerization, the Lewis acids used could be classified mainly into three categories in terms of polymerization behavior: those producing long-lived species (e.g., MoCl5, NbCl5, and ZrCl4), those inducing uncontrolled polymerization (e.g., GaCl3 and FeCl3), or those showing no activity at all (e.g., ZnCl2 and InCl3). The matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI−TOF−MS) spectra of the product polymers and the direct 1H NMR analysis of the reaction mixtures revealed that the controlled polymerization sta...

Living Cationic Polymerization of Vinyl Ether with Methanol/Metal Chloride Initiating Systems: Relationship between Polymerization Behavior and the Nature of Lewis Acids

Es wird gezeigt, das die Reaktion zwischen Molybdanpentachlorid und Methylalkohol in zwei Richtungen verlaufen kann. Die Reaktionsprodukte werden beschrieben.



It is shown that the reaction between molybdenum pentachloride and methanol proceeds in two ways. The resulting compounds are described.

F. Schmeil

Papers

Die Methanolyse des Molybdänpentachlorids. II